Identification and Analysis of Points of Diversion along the Lower Colorado River in Support of Decree Accounting

Science Center Objects

 In the United States, the Colorado River Compact of 1922 apportions the waters of the Colorado River between the upper basin States and the lower basin States (U.S. Congress, 1948, p. A17-A22). The requirement for participation of the U.S. Geological Survey (USGS) and the Bureau of Reclamation (BOR) is stated in Article V. Water in the lower Colorado River is apportioned among the States of California, Arizona, and Nevada by the Boulder Canyon Project Act of December 21, 1928 (U.S. Congress, 1948, p. A213-A225) and confirmed by the U.S. Supreme Court decree, 1964, Arizona v. California in terms of consumptive use. The decree is specific about the responsibility of the Secretary of the Interior to account for consumptive use of water from the mainstream; consumptive use is defined to include "water drawn from the mainstream by underground pumping."

The Decree requires the identification of the users of Colorado River water and publication of the quantities of diversion and consumptive use stated for each diverter, point of diversion, and State. The BOR (1965-2004) publishes an annual report that contains records of diversions and consumptive use of water by individual water users. Much of the hydrologic information contained in the annual report is furnished by the USGS (Condes de la Torre, 1982, p. 5-7). A method is available for identifying wells that yield water that will be replaced by water from the river and wells that yield water that will be replaced by water from precipitation or inflow from adjacent tributary valleys (Wilson and Owen-Joyce, 1994; Owen-Joyce and others, 2000).

Accounting for the consumptive use of Colorado River water withdrawn from the river aquifer by wells requires that updated information for each well within the boundary of the river aquifer between the northeast end of Lake Mead to the international boundary with Mexico (see map) be collected in order to apply the accounting-surface method, which is used to identify those wells that yield water that will be replaced by water from the river.

Implementation of the method to identify wells along the lower Colorado River that yield water that will be replaced by water from the river will enable the Secretary of the Interior to fulfill a responsibility to account for consumptive use of water from the mainstream by underground pumping. The updated data set will provide the needed framework from which to investigate other hydrologic concerns and produce interpretative hydrologic products such as more current water-level maps in areas where sufficient data are available and maps that show zoned areas where static-water levels are, for example, more than 50 feet above the accounting surface needed for management decisions.

Objective

Map of study area for the Lower Colorado River decree accounting project

Map of the study area for the identification and analysis of points of diversion along the Lower Colorado River in support of degree accounting.

Present accounting for consumptive use of Colorado River water is incomplete because the existence and location of all points of diversion is not known. Of the more than 4,000 wells previously identified between 1960 and 1993, information such as the ownership, elevation of water level, use of water, disposal of unconsumed water, and well construction information generally require updating. A precise position is required for all new sites in addition to those previously identified in order to assure that the correct site is revisited for future data collection. River pumps are a direct diversion of water from the mainstream of the Colorado River and need to be included in accounting for diversions under the Decree and for consumptive use.

The objective of this work is to identify and locate wells that have the potential to pump water that will be replaced by water from the Colorado River and river pumps that pump directly from the mainstream; and to acquire, record, and store for future retrieval, the data and information needed to determine or "presume" if a well is pumping water that will be replaced by water from the Colorado River and therefore included in the accounting of Colorado River water use mandated by the Decree. USGS will identify sites in the area from the mouth of the Grand Canyon at Lake Mead to the southerly international boundary with Mexico that exist within the river aquifer as defined in the accounting surface methodology reports (Wilson and Owen-Joyce, 1994; Owen-Joyce and others, 2000).

 

Approach

Identify, locate, collect required data, and enter into the Geological Survey National Water Information System (NWIS) (or successor) database wells with the potential to pump water that will be replaced by water from the Colorado River, along with data necessary to determine or "presume" if these wells are indeed pumping water that will be replaced by water from the Colorado River, and data which will assist in estimating the type and quantity of water use. River pumps will be identified and located; required data will be collected in a manner similar to wells. A photograph of each well and river pump will also be recorded and stored in a database for future retrieval to assist in returning to the well or river pump. Data collected will be used in the analysis required to determine or "presume" if the well is pumping water that will be replaced by water from the Colorado River, the type of water use, and assist with estimating the magnitude of water use.

The USGS project manager attends meetings at Reclamation’s request to provide technical and scientific coordination with Reclamation staff, other agencies, and the public. Under the supervision of the project manager, the USGS will send trained technicians into the field to,

  1. coordinate with appropriate permitting agencies as needed to obtain locations of known permitted well sites;
  2. visit identified potential well sites and collect data at wells that have been drilled or record that no well has yet been drilled;
  3. investigate areas for signs of development that indicate water use, and identify and collect data at wells and/or river pumps in use in those areas;
  4. photograph each well/river pump and measure water levels in wells in the areas where the accounting surface was developed and access is possible;
  5. enter wells and river pumps into the Geological Survey NWIS database (or successor database) without creating duplicate sites in the database;
  6. determine when data collection for all sites in an area is completed and identify (with input from Reclamation) subsequent areas for data collection, and plan effective strategies to meet project objectives;
  7. determine (with input from Reclamation) wells to be instrumented for continuous water-level data collection, purchase equipment as needed, construct and install instrument protective housing at well sites, collect and process data, store data in NWIS;
  8. continue to collect, process, and store data from wells already instrumented for continuous water-level data collection;
  9. prepare maps showing altitude of the water table and areas where the water table is more than 50 feet above the accounting surface after precise differential GPS data collection is completed; maps will be published on the web and merged with the data on the interactive web page;
  10. prepare an interactive web page to visibly display the data collected and merge with the accounting surface maps developed previously in cooperation with Reclamation;
  11. report progress to Reclamation, coincident with Geological Survey project reviews and create annual work plans for the coming year with input from Reclamation.